Field of the Invention
The present invention relates to a resin composition and a prepreg and laminate prepared using the same. Specifically, the present invention relates to a resin composition useful for preparing a laminate with a high dielectric constant (Dk) and low dielectric loss.
Descriptions of the Related Art
Printed circuit boards (PCBs) are circuit substrates that are used for electronic devices to load other electronic components and to electrically connect the components to provide a stable circuit working environment. One kind of conventional printed circuit board is a copper clad laminate (CCL), which is primarily composed of resin(s), reinforcing material(s) and copper foil(s). Conventional resins include epoxy resins, phenolic resins, polyamine formaldehyde resins, silicone resins or polytetrafluoroethylene resins. Conventional reinforcing materials include glass fiber cloths, glass fiber mats, insulating papers or linen cloths.
In general, a print circuit board can be prepared by using the following methods: immersing a reinforcing material, such as glass fiber fabric into a resin (e.g. epoxy resin), and curing the immersed glass fiber fabric into a half-hardened state to obtain a prepreg; superimposing certain layers of the prepregs and superimposing a metal foil on at least one external surface of the superimposed prepregs to provide a superimposed object; hot-pressing the superimposed object to obtain a metal clad laminate; etching the metal foil on the surface of the metal clad laminate to form a defined circuit pattern; and finally, drilling a plurality of holes on the metal clad laminate and plating these holes with a conductive material to form via holes to accomplish the preparation of the printed circuit board.
As the size of the electronic devices becomes smaller, PCBs must be thinned and made more densely to include much more active and passive components. In view of this, component-functional areas must be formed within a laminate to allow for more freedom in the circuit design. A radio frequency (RF) field especially requires highly dense PCBs. This is because the use of a laminate with excellent electrical properties (high dielectric constant and low dielectric loss) to incorporate a passive component into the laminate will allow a general radio frequency modules and digital system to be incorporated into one single PCB. Unfortunately, the dielectric loss of a laminate prepared by epoxy resin is still high (Df is high), and the dielectric constant (Dk) of the laminate also fails to meet the requirements of a capacitor material. As a result, the industry has been trying to develop a dielectric material which is low-cost, but has excellent electrical properties (high Dk and low Df).
TW 200927806 discloses a low dielectric loss composition for a flexible substrate, which improves the dielectric constant of the composition by adding ceramic powders of strontium titanate (SrTiO3) and/or barium strontium titanate (BaSrTiO3) with a particle size ranging from 30 nm to 2 μm. However, the improvement is very limited.
US 2004147658 discloses a composition for the formation of a built-in capacitor layer of a printed wiring board, which includes a dielectric powder with a particle size ranging from 0.1 μm to 2 μm, such as barium titanate (BaTiO3) and strontium titanate (SrTiO3). The composition is still prepared based on an epoxy resin system. The dielectric loss (Df) is therefore still high.
U.S. Pat. No. 7,700,185 discloses an insulation composite material, which is primarily composed of a filler with a high dielectric constant and insulation resin (mostly epoxy resin). The filler must be a ceramic powder with a bimodal particle size distribution. A dispersant must be used to help disperse the powder. As can be seen from the illustrated examples, the insulation composite material still has a high Df (up to 0.02).
In view of this, the present invention provides a resin composition which does not require a dispersant and is useful in preparing a laminate with a low Df value and high dielectric constant.